Thyroid cancer is the most common classical endocrine malignancy, and its incidence has been rising rapidly in the US as well as other industrialized countries over the past few decades. Thyroid cancers are classified histologically into four groups: papillary, follicular, medullary, and undifferentiated or anaplastic thyroid carcinomas. If diagnosed at an early stage, thyroid cancer is a well manageable disease with a 5-year survival rate of 97% among all patients. Survival rate is poorer (about 40%) among individuals that are diagnosed with a more advanced disease; i.e., individuals with large, invasive tumors and/or distant metastases have a 5-year survival rate of about 40%. For radioiodine-resistant metastatic disease, there is no effective treatment and the 10-year survival rate among these patients is less than 15%.
Although relatively rare (1% of all malignancies in the US), the incidence of thyroid cancer more than doubled between 1984 and 2004 in the US. Between 1995 and 2004, thyroid cancer was the third fastest growing cancer diagnosis, behind only peritoneum, omentum, and mesentery cancers and “other” digestive cancers. Similarly, dramatic increases in thyroid cancer incidence have also been observed in Canada, Australia, Israel, and several European countries. Thus, there is a need for better understanding of the molecular causes of thyroid cancer progression to develop new diagnostic tools and better treatment options.